Gas generators are known that include an igniter and a compressed gas container which contains a first filling gas and has an outflow opening that is closed by a bursting diaphragm, where the igniter produces a shock wave upon activation of the gas generator and the shock wave runs at least in part through the compressed gas container before destroying the bursting diaphragm.
Following the destruction of the bursting diaphragm, the first filling gas and also the gas generated from the propellant charge associated with the igniter upon ignition thereof escape from the gas generator through the outflow opening to fill a gas bag or to drive a mechanical device such as a belt tensioner, for example.
In principle, there exist two different approaches to cause the bursting diaphragm to be opened due to the internal pressure of the compressed gas container. In the first case, the internal pressure within the entire compressed gas container is raised relatively homogeneously and relatively slowly by an increase in temperature until the internal pressure exceeds the bursting pressure of the bursting diaphragm. In the second case, a shock wave is produced, e.g., by the igniter, the shock wave running through the compressed gas container and impinging on the bursting diaphragm. In this case, the pressure at the bursting diaphragm is raised above the bursting pressure only locally and momentarily, whereas a distinctly lower pressure prevails in the remaining part of the compressed gas container. The advantage of the shock wave technique resides in that a rapid opening of the bursting diaphragm is obtained since the shock wave reaches the bursting diaphragm very fast.
An impulse transmitted by a shock wave is the higher the heavier the particles of the substance that is traversed by the shock wave. The velocity of flow of the gas out of the gas generator, however, is the higher the lighter the filling gas.